gistfile1.ml

Tests:

    [<Test>]
    let should_throw_exception_if_feed_xml_is_invalid () =
        Assert.Throws<FailureException>(fun () -> FeedBurners.ProcessFeed "some broken xml" |> ignore) |> ignore
        
    [<Test>]
    let should_throw_exception_if_no_feed_found () =
        let feedXml = @"<?xml version=""1.0"" encoding=""utf-8"" ?>
                        <rsp stat=""fail"">
                            <err code=""1"" msg=""Feed Not Found"" />
                        </rsp>"
    
        Assert.Throws<FailureException>((fun () -> FeedBurners.ProcessFeed feedXml |> ignore), 
                                        "Failed to process feed: Feed Not Found") |> ignore   
                                        
    [<Test>]     
    let should_retrieve_circulation_and_date_if_valid_xml () =
        let feedXml = @"<?xml version=""1.0"" encoding=""UTF-8""?>
                        <rsp stat=""ok"">
                            <feed id=""tdv0bg210cr731gc3nssn512cg"" uri=""MarkNeedham"">
                                <entry date=""2009-07-16"" circulation=""630"" hits=""1389"" reach=""629"" />
                            </feed>
                        </rsp>"
        
        let entries = FeedBurners.ProcessFeed feedXml
        let entry = entries |> Seq.hd
        
        Assert.AreEqual(entry.Circulation, 630) 
        Assert.AreEqual(entry.Date, "2009-07-16") 

Code:

    let xName value = XName.Get value
    let GetDescendants element (xDocument:XDocument)  = xDocument.Descendants(xName element)
    let GetAttribute element (xElement:XElement) = xElement.Attribute(xName element)          
    type FeedBurnerApi = { Date : string; Circulation : decimal}
    
    let (|NoFeedFound|FeedBurnerStats|) xml = 
        try 
            let document = xml |> XDocument.Parse
            let entries = document |> 
                          GetDescendants "entry" |> 
                          Seq.map (fun element -> GetAttribute "circulation" element, GetAttribute "date" element) |>
                          Seq.map (fun attribute -> { Circulation =  Decimal.Parse((fst attribute).Value); 
                                                      Date = (snd attribute).Value } )
            
            match Seq.length entries with 
                | 0 -> NoFeedFound((document |> GetDescendants "err" |> Seq.hd |> GetAttribute "msg").Value)
                | _ -> FeedBurnerStats(entries)
        with 
            | :? System.Xml.XmlException as ex -> NoFeedFound(ex.Message)
            
    let ProcessFeed xml =
        match xml with 
            | NoFeedFound(error) -> failwith ("Failed to process feed: " + error)
            | FeedBurnerStats(entries) -> entries